Likutei Moharan 75:13/ליקוטי מוהר"ן ע״ה:י״ג

113. A person must speak words of Torah and prayer until he negates and nullifies the body. This is as in “and they become one flesh” (Genesis 2:24)—the body should become one with the speech. {This is the aspect of ChaVaH, as it is written (Psalms 19:3), “and night to night ye’ChaVeH (speaks out) knowledge,” as was explained elsewhere. She is the aforementioned tzela, the aspect of “[God] built the rib,” concerning which it is said: “and they become one flesh.”} In other words, the body should be completely negated by means of words of Torah and prayer, as if it were nullified and non-existent.

2The way to achieve this utter negation of the body is through fear. As our Sages, of blessed memory, taught: The body is powerful, [but] dread breaks it (Bava Batra 10a). And “dread” is the aspect of “the Dread of Yitzchak” (Genesis 31:42)—i.e., fear.